1. Field of the Invention
The present invention relates to Early effect canceling circuit and Early effect canceling method, and more particularly to circuit and method capable of preventing current generated by Early effect from appearing in output current of current mirror circuit.
2. Description of the Related Art
If current variation components due to Early effects are contained in the input current flowing in the current mirror circuit, its effects directly appear in the output current of the current mirror circuit. Accordingly, this current mirror circuit is explained as an example of using in DC-DC converter of linear regulator system.
In laptop and other portable electronic appliances, batteries are used as power source for appliances, but the battery voltage generally declines as discharge progresses, and it is attempted to stabilize the battery output voltage by using a DC-DC converter in order to keep constant the voltage used in the electronic appliance. In the case of a small output current capacity, a linear regulator is often used in relation to the physical size of DC-DC converter or cost of choke coil. A linear regulator of small capacity is composed of one-chip semiconductor, and the physical size is small and the cost is low. If the input and output voltage ratio is small, the efficiency of linear regulator is a sufficiently practical value. In particular, in sound source circuit or the like where switching noise must be eliminated, the linear regulator is preferably used.
In prior art documents investigated before filing of the present application, no information relating to the invention of the present application has been discovered in publications, papers and other documents printed, filed or disclosed prior to the present application. Hence, the present application cites no prior art and document information.